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IC 


9006 



Bureau of Mines Information Circular/1985 



Safety Aspects of Pneumatic Transport 



By E. T. Bowers 




UNITED STATES DEPARTMENT OF THE INTERIOR 



'^;NES75TH AXA'^ 



Information Circular 9006 



Safety Aspects of Pneumatic Transport 



By E. T. Bowers 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Model, Secretary 

BUREAU OF MINES 
Robert C. Morton, Director 




<> 






D' 







^ 



0' 



Library of Congress Cataloging in Publication Data: 



Bowers, E. T. (Elaine T.) 










Safety aspects of pneumatic transport. 










(Bureau of Mines information circular ; 


9006) 








Bibliography: p. 35-37. 










Supt. of Docs, no.: I 28.27:9006. 










1. Pneumatic-tube transportatiort— Safe 


ty measures. 2. 


Mine haul- 1 


age— Safety measures. 3. Coal mines and 


mining- 


-Safety measures. 


I. 


Title. II. Series: Information circular 


(United States. 


Bureau 


of 


Mines) ; 9006. 










-*l'«&&.-¥4- [TN813] 622s [622' 


.8] 


84-600211 





C CONTENTS 









Page 



Abstract 1 

Introduction 2 

Acknowledgments 3 

Background 3 

History of pneumatics In mining 4 

Safety analysis of conventional haulage systems 6 

Shuttle cars 7 

Conveyors 10 

Skip hoisting , 12 

Rail haulage 15 

Safety and hazard analysis of pneumatic transport 20 

Methane-air mixture 21 

External coal dust 22 

Static electricity 23 

Thermite reaction 24 

Noise 24 

Pneumatic alternatives to conventional haulage 25 

Off-loading a continuous-mining machine 25 

Vertical hoisting 30 

Off-loading a tunnel boring machine 32 

Conclusions 34 

References 35 

ILLUSTRATIONS 

1 . Pneumatic haulage on room-and-plllar section 28 

2. Feeder, breaker, and bunker conveyor for vertical hoisting 30 

3. Layout plan for pneumatic vertical hoisting 31 

4. Layout of pneumatic transport off-loading a tunnel-boring machine 33 

TABLES 

1. Analysis of shuttle car accidents 8 

2. Hazard analysis of a shuttle-car haulage system 11 

3. Analysis of conveyor accidents 13 

4. Hazard analysis of skip hoisting system 16 

5. Analysis of rail haulage accidents 17 

6. Hazard analysis of a rail haulage system 19 

7. Hazard analysis of a pneumatic haulage system off-loading a contlnuous- 
mlnlng-machlne section 26 

8. Hazard analysis of a pneumatic haulage system for vertical hoisting 27 

9. Hazard analysis of a pneumatic haulage system to off-load a tunnel-boring 
machine 27 

^ 10. Cost estimate of a pneumatic hoisting system 32 

"J||^ 11. Cost estimate of a vertical hoisting system 33 

12. Cost estimate of pneumatic conveying system to off-load a tunnel-boring 

machine 34 

^ 13. Cost estimate of a rail haulage system 34 





UNIT OF MEASURE ABBREVIATIONS USED 


IN 


THIS REPORT 


cfm 


cubic foot per minute 


ym 




micrometer 


yd^ 


cubic yard 


pet 




percent 


dB 


decibel 


psi 




pound per square inch 


ft 


foot 


rpm 




revolution per minute 


ft/h 


foot per hour 


ton/h 




ton per hour 


hp 


horsepower 


ton/min 


ton per minute 


in 


inch 


yr 




year 


lb 


pound 









SAFETY ASPECTS OF PNEUMATIC TRANSPORT 

By E, T. Bowers' 



ABSTRACT 

Pneumatic conveying of coal underground is not widely used in the 
United States , although it is becoming increasingly popular in Great 
Britain, the Federal Republic of Germany, and South Africa, The ques- 
tion of safety has been raised repeatedly: Will the system be prone to 
dust or gas explosions, and, if so, can it withstand such occurrences 
safely? 

The work reported here was done under a Bureau of Mines contract and 
deals with the safety aspects of pneumatic transport of underground 
coal, as well as the hazards inherent in more conventional haulage sys- 
tems. Included are three designs for different applications of pneu- 
matic haulage: off-loading a continuous-mining machine on a room- 
and-pillar section, vertical hoisting through a 1,200-ft shaft, and 
off-loading a tunnel-boring machine driving a 2,000-ft tunnel. 



^Statistician, Spokane Research Center, Bureau of Mines, Spokane, WA, 



INTRODUCTION 



Haulage of coal or rock out of a mine 
is a major part of a mining operation. 
Rapid excavation and high production are 
impossible if a haulage system, particu- 
larly a face haulage system, cannot keep 
pace with mining rates. Also, under- 
ground haulage can be dangerous. A look 
at accident statistics gathered over the 
last several years by the Health and 
Safety Analysis Center (HSAC) , a branch 
of the Mine Safety and Health Administra- 
tion (MSHA) , U.S. Department of Labor, 
shows a disproportionate number of seri- 
ous lost-time accidents involving haul- 
age. From 1978 through 1980, haulage 
accounted for only 10.5 pet of all acci- 
dents, but was responsible for 21.9 pet 
of the total relative risk, and 27.4 pet 
of all the fatalities. These statistics 
were developed by the Bureau's Spokane 
Research Center's (SRC) accident data 
analysis (ADA) program (1).^ Risk is 
defined here as the sum of the conse- 
quences, or severity, times the probabil- 
ity of occurrence. Using the severity of 
the accidents, measured by total time 
lost to compute "risk," provides a much 
better indication of the importance of 
those accidents. In other words, fatali- 
ties and cut fingers no longer have the 
same significance. 

In recent years, experimentation has 
been conducted using pneumatic systems 
for underground haulage. Pneumatics has 
already established its place in such 
industries as shipping, loading and un- 
loading of grain, chemicals, wood chips, 
etc. , and in manufacturing by deliver- 
ing supplies or chemicals inside a plant, 
or carrying fuel to blast furnaces. The 
use of pneumatics in the mining indus- 
try, however, has been limited largely 
to the stowing of waste or backfill or 
the conveying of rock dust or concrete. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this report. 



European countries have pioneered the use 
of pneumatics to haul coal or waste out 
of the work area and the mine. In the 
1970' s, several British collieries in- 
stalled pneumatic haulage systems to re- 
lieve overloads on their hoisting sytems. 
The success of pneumatics was apparent 
immediately. Production rates increased, 
haulage costs decreased, and development 
of new shafts proceeded without halting 
the mining of coal. 

There have been several studies con- 
ducted in the United States on pneumatic 
haulage of coal, mostly under the direc- 
tion of the Bureau. The major concern 
has been the danger of fire or explosion 
of gases trapped within the system, which 
could be set off by sparking of coal or 
by a rock glancing off the pipeline at 
high speeds. This hazard has been stud- 
ied extensively; consequently, safety 
precautions were prescribed and tested. 

Increasing interest in pneumatic haul- 
age, particularly for new mines or those 
with difficult or unusual haulage prob- 
lems , resulted in a Bureau contract with 
Radmark Engineering in December of 1979. 
The purpose of the contract was to design 
pneumatic transport systems to hoist ma- 
terial, off-load a tunnel-boring machine 
(TBM), convey either to an in-mine con- 
veyance system or directly to the surface 
through a borehole, and to off-load a 
face-mining machine. All designs were to 
be safer than existing conveying systems. 
Hazard analyses were to be included. The 
final report (2^) , submitted in January 
1981, became the basis for this report. 

This report discusses the background 
and history of pneumatic haulage relating 
to underground coal, brief accident and 
hazard analyses of the main types of 
haulage used in the United States , hazard 
analyses of various applications of pneu- 
matic transport, and pneumatic alterna- 
tives to three haulage systems. 



ACKNOWLEDMENTS 



Work presented by Eric Powell of Rad- 
mark Engineering, Inc. , under Bureau of 
Mines contract JO100029, was used as ref- 
erence for this report. All of the 



illustrations and several tables included 
herein were taken from the final report 
of that contract. 



BACKGROUND 



Conveying materials into a mine, and 
waste or coal out of a mine, has tradi- 
tionally been done by rail, conveyor, or 
rubber-tired equipment. The use of pneu- 
matics has generated much interest in 
the past 20 yr, for reasons as varied as 
economy, flexibility, relative simplic- 
ity, and safety. 

Pneumatic conveying can be described 
as a materials-handling system that uses 
the flow of air or gas to move parti- 
cles through a pipeline by maintaining a 
pressure differential between the ends 
(3). It may be a simple fan system or 
the more complex blower systems that 
include rotary, positive, and oil-free 
blowers, among others. 

Any pneumatic system consists of three 
main parts: (1) the air source, (2) the 
feeder, which moves the material from at- 
mospheric pressure to the high or low 
pressure inside the conveying pipe, and 
(3) the pipeline, which conveys the mate- 
rial to the surface or discharge point. 
Other peripheral components may be nec- 
essary, such as crushers or sizers, a 
feeder conveyor, discharge cyclones, si- 
lencers, etc. 

There are three types of material flow 
within a pneumatic pipeline: stream 
flow, two-phase flow, and slug flow. 
Streamflow (sometimes called dilute phase 
flow) occurs when the air velocity is 
high enough and the ratio of solids-to- 
air is low enough that the material is 
suspended in a stream of air. Two-phase 
flow (dense-phase flow) occurs when the 
air velocity is not sufficient or the 
air-to-solids ratio is too high to move 
the material totally suspended in air. 
In this type, solids settle out into a 
bed that is either motionless at the 



bottom of the pipe, or dragged along, 
while streamflow conveying is taking 
place above. In systems with high total 
pressure differentials, the conveyed ma- 
terial may be in two-phase flow at the 
beginning of the pipe, and streamflow at 
the end. Slug flow (piston flow) occurs 
when conveyed materials retain enough 
fluidity to be pushed through the pipe- 
line by pressure alone. 

The three types of pneumatic systems 
are named according to fan location: 
downstream, upstream, and pull-push. 
Downstream, or pressure systems (posi- 
tive) , are simple systems that cannot 
harm the fan but that have the disadvan- 
tage that any leaks are outward from the 
system. Positive pressure systems intro- 
duce material into the pipeline through a 
rotary feeder or two-door discharge gate; 
it is then pushed through the pipe to the 
discharge point. Pickup is controlled, 
and delivery over long distances is pos- 
sible. Upstream, or vacuum systems (neg- 
ative) , provide the simplest and most 
flexible material pickup and the best 
dust control. Disadvantages include lim- 
ited range and placement of the fan in a 
vulnerable position. The pull-push sys- 
tem, has the advantages of both of the 
first two, but is restricted to nonabra- 
sive materials that will not be damaged 
by passage through the fan. 

Any of the systems having low pressure 
are most often used with large-particle 
materials. Fan-type pneumatic systems 
are generally used for nonabrasive mate- 
rials of large particle size and low 
density that are conveyed downstream, up- 
stream, or through the fan. The pneumat- 
ic systems discussed in this report will 
be, for the most part, limited to low 
pressure, positive systems. 



HISTORY OF PNEUMATICS IN MINING 



Pneumatic systems have been used since 
the 1930* s in Belgium, Holland, Germany, 
the United Kingdom, and other parts 
of Europe to convey waste material to 
worked-out areas of mines. The Markham 
and Co., Ltd., of the United Kingdom, de- 
signed and built a stowing machine in 
1942; and in the process of testing and 
refining their design, did extensive 
tests on pipelines, particularly the de- 
sign of bends or elbows in order to mini- 
mize wear. Although the original purpose 
of their work was to design a stowing ma- 
chine, the benefits to be gained from 
vertical pneumatic hoisting soon be- 
came obvious. Work was done in the early 
1950' s by the mining department of Leeds 
University to determine air velocities 
needed to lift mine materials over vari- 
ous distances (4^). In 1958, the National 
Coal Board installed simple systems in 
several collieries to move debris from 
one level to another. 

The use of pneumatics for mining took 
on more importance in 1966 when a group 
of pneumatics experts and a Canadian min- 
ing company collaborated to design a sys- 
tem that could economically handle large 
amounts of minus 3-in hard, abrasive ig- 
neous rocks over distances up to 2,500 
ft. With this project, pneumatic systems 
were designed and used for stowing and 
for haulage and hoisting in mines. 

The first commercial use of pneumatic 
conveying in North America tested the' 
newly designed equipment in 1968 on a 
tunnel-boring project in the city of 
Edmonton, Alberta, Canada (_5-6). Con- 
ventional track haulage was restricting 
excavation efficiency of the mole to 
43 pet or less. Because the tunnel was 
only 7 ft in diameter for over 50 pet 
of its length, there was no room for Cal- 
ifornia switches and the two-track sys- 
tem that would have normally handled the 
cuttings. Many alternative systems were 
considered, but all had drawbacks: the 
physical size of a hydraulic haulage 
system precluded its use, curves in 
the tunnel made conveyors impractical, 
and there was inadequate ventilation for 
diesel haulage. A pneumatic system was 



installed through existing boreholes that 
had been drilled every 800 ft for align- 
ment and delivery of power and water to 
the mole. Although the system was not 
100 pet successful due to buildup of 
sticky clay in the feeder and subsequent 
jamming of the feeder by oversize cut- 
tings, the trial proved that pneumatic 
conveying was possible, given that the 
material conveyed was suitable. Five 
years later, a similar application was 
used in Halifax, Nova Scotia, where cut- 
tings were conveyed 2,000 ft horizontal- 
ly and 200 ft vertically. This test was 
considered successful, delivering a 95- 
pct availability of the haulage system to 
the tunnel borer (6) . 

In 1972, Comlnco , Ltd., of Canada, in- 
stalled a trial vertical hoisting system 
at their Sullivan Mine in Kimberly, Brit- 
ish Columbia. Mine wastes minus 3 in to 
plus 1/4 in were transported successfully 
at a rate of 40 ton/h (_5 ) . Information 
gained in this test led the way for a 
combined test in England by Radmark Engi- 
neering and the British National Coal 
Board. 

Horden Colliery was chosen as the site 
for a high-lift trial. British coal pro- 
duction was severely hampered by the 
fact that many of the hoist systems had 
reached full capacity. The development 
of new haulage shafts was complicated by 
the presence of thick seams of water- 
bearing rock that had to be frozen during 
shaft development, making shaft sinking 
costly, difficult, and time-consuming. 
It was possible, however, to add pneu- 
matic systems to existing shafts with- 
out interfering with mining or hoisting 
activities. The Horden test used an ex- 
isting 8-in-diam pipe to lift coal verti- 
cally a distance of 1,268 ft. The test 
was considered successful because the 
system performed as expected with no ma- 
jor problems (_7 ) . 

As a result of the success of the 
Horden test, two more trials were set 
up by the National Coal Board: one at 
Shirebrook in North Derbyshire, start- 
ing in 1977 (7-8); and one at Fryston in 



North Yorkshire in 1977-78. In the opin- 
ion of the researchers, the pneumatic 
systems never reached full potential, but 
they still were able to increase mine 
production by 25 pet. 

Pneumatic applications in U.S. coal 
mines have been limited to backfilling or 
stowing, but their use is growing. The 
Alaska Pipeline, for instance, used pneu- 
matics to transport and place packing 
material around the pilings for the pipe- 
line and around the pipeline itself, 
and to convey and place materials when 
weather and terrain precluded the use of 
more conventional methods (6) . Perhaps 
the first major U.S. test of pneumatic 
conveying for mining was in 1974 when 
McCarthy Engineering used it to help re- 
novate the Bureau's Bruceton Experimental 
Mine. Twelve thousand yards of muck had 
to be transported 2,8 50 ft out of the 
mine and then to a muck pile, A conven- 
tional muck car system was considered but 
ruled out when it was estimated that a 
pneumatic system would be much cheaper. 
The system eventually installed operated 
at an estimated cost of only 25 pet of 
the conventional system (9^). Faddick and 
Martin ( 10 ) report Colorado School of 
Mines tests on conveying tunnel muck for 
the purpose of gathering data on reli- 
ability and flexibility, wear and mainte- 
nance requirements, capacity, noise and 
dust levels, energy requirements, effect 
of moisture content, and extensibility. 
Their conclusions support use of pneu- 
matic conveying if costs are competitive. 

Rochester & Pittsburgh Coal Co. (R&P) 
made use of pneumatics in 1980 in one of 
the first commercial applications in the 
United States to transport cuttings from 
a tunnel borer, A 1,200-ft tunnel was 
driven to connect the company's Urling 
Nos. 1 and 3 Mines, and a pneumatic con- 
veying system carried the 16,500 tons of 
waste rock out of the mine. R&P plans to 
continue using pnevimatics to eliminate 
underground gobbing and skip hoisting of 
rock (jj^). 

The first commercial use of pneumat- 
ics in the United States with a shaft- 
sinking operation occurred in 1980 at 



Island Creek's Providence No. 1 Mine. By 
using a slusher, grizzly ramp, and pneu- 
matic blower system and operating with a 
raise-borer, managers were able to sub- 
stantially reduce time and cost by elimi- 
nating any handling of cuttings through 
the mine (12). 

In 1982, Garfield Energy Co. of Colo- 
rado became the first U.S. mine to use 
an underground conveying system for pri- 
mary haulage. With a 40° slope and a 
fairly small production (50-60 tons/h) , a 
system was needed that was both efficient 
and inexpensive. The system designed by 
Pneumatic Transportation Systems, Inc., 
met these requirements (13-14) . 

The use of a pneumatic vacuum system 
has also made it possible for a small 
mine in Alabama to continue operation. 
Faced with the problem of mining a 24-in 
seam economically, the Cash No. 1 Mine 
was closed because of the expense and 
time involved in haulage. The coal had 
to be drilled, blasted, hand-shoveled 
onto a panline, and hauled 200 ft by a 
scoop. Using this system, 28 workers 
were only able to mine 40 tons per shift. 
When a vacuum face haulage system was in- 
stalled, however, the same job was han- 
dled by only five miners. In addition to 
increasing haulage capacity and cutting 
mining time, the mine owner claims a cost 
reduction of 90 pet and improved safety 
(15). 

Another application of vacuum haul- 
age was in conjunction with the develop- 
ment of the blind shaft borer (BSB). The 
BSB, designed and tested under the aus- 
pices of the Bureau and the U.S. Depart- 
ment of Energy, was essentially a tunnel- 
boring machine turned on its nose. It 
was designed to sink a 24-ft-diam shaft 
at a steady rate of 50 ft per day to a 
depth of 2,000 ft. The major problem was 
removing the cuttings that accumulated 
at a rate of 200 ton/h when the machine 
maintained an advance rate of 5 ft/h, 
Radmark Engineering was awarded a con- 
tract in 1978 to develop a vacuum pick- 
up system. The field tests of the BSB 
were halted before completion; how- 
ever, the tests of the vacuum pickup, run 



separately, were successful, showing that 
vacuum systems could remove up to 220 
ton/h, regardless of the moisture content 
of the muck (16). 

Currently, interest in pneumatic con- 
veying in the United States is growing. 
Powell ( 17) , an expert in the field of 
pneumatics, states, "We expect to see 
a major increase in the application of 
pneumatic conveying equipment in the U.S. 
mining industry, not only as an extension 
of , , . hoisting rock from tunnel-boring 
machines and raise boring machines , but 
also in the transfer of waste material 
into mines for roof-control purposes and 
also to avoid the necessary buildup of 
waste of the surface ..." There is 
little question that cost and efficiency 
are decisive factors in this trend. Many 
studies have been conducted on costs, 



engineering data, and equipment. Costs 
and designs are, of course, variable, de- 
pending largely on the size, expected 
capacity, and application of the system 
required. Many of the major manufac- 
turers of pneumatic haulage systems have 
prepared extensive reports detailing 
their available equipment, and projecting 
such factors as costs, capital and labor 
wear, power requirements, etc. 

A serious question in pneumatic coal 
conveying concerns the safety aspects. 
The last 20 yr have seen the use of pneu- 
matics expand, especially in European 
mines, with few, if any, added safety 
problems. Numerous studies have been 
conducted, however, on safety. These 
will be summarized and expanded upon in 
this report. 



SAFETY ANALYSIS OF CONVENTIONAL HAULAGE SYSTEMS 



In order to better understand the prob- 
lems of underground haulage, particularly 
those that are safety related, short ac- 
cident and hazard analyses of four types 
of haulage common to underground U.S. 
coal mines are presented here, including 
(1) shuttle cars, (2) conveyors, (3) ver- 
tical skip hoisting, and (4) rail haul- 
age. These methods represent a wide var- 
iety of haulage systems and are meant to 
be taken as "generic" in that they are 
broad, generalized categories. 

The accident analyses included are, 
based entirely on accident statistics 
taken from the HSAC data files. Because 
these data were not gathered for the spe- 
cific purpose of accident analysis, there 
are obvious omissions and exclusions. 
For instance, rail and skip haulage are 
two-directional; i.e., they carry coal 
and waste out of the mine, as well as 
bring supplies and, occasionally, miners 
in. In some mines, conveyors also could 
be considered two-directional, yet the 
accident statistics do not differentiate 
between production haulage and supply or 
transportation haulage. 

A major problem in using accident 
statistics is the absence of usable 



production data that would help "normal- 
ize" the statistics; i.e., accidents or 
"risk" per ton of coal hauled. Without 
this information, it is very difficult 
to accurately compare different haulage 
methods. The number of accidents 
attributable to each method is known, as 
well as their severity. No information 
is available, however, on how many shut- 
tle cars, for instance, were in opera- 
tion, how many operators there were, how 
much time they spent actually hauling 
coal, or how many tons of coal they car- 
ried. For this reason, there is a built- 
in bias to any analysis of this type. 
Another problem occurs in trying to 
relate these haulage methods and their 
statistics to pneumatic haulage that 

(1) has no known accident statistics, 

(2) is a totally one-directional system, 
and (3) has not been used to any degree 
for underground coal haulage in the 
United States. In other words, compari- 
sons may be set up between the safety 
aspects of pneumatics and conventional 
haulage, but they are, for the most part, 
speculative. 

Hazard analysis, another method of 
safety analysis, has been included for 
shuttle cars, skip hoisting, rail haulage 



(relevant to off-loading a tunnel borer), 
and for the three pneumatic systems de- 
signed to replace these haulage methods. 
(No hazard analysis was available for 
conveyor haulage.) Hazard analysis, a 
relatively recent development, focuses on 
the accident potential of hazards before 
accidents occur. In this way, it is of a 
preventive nature rather than a retro- 
spective one. This method was developed 
in the aerospace and nuclear industries. 
Hazard analysis usually involves a total 
system rather than particular conditions 
or circumstances; for example, the rela- 
tionship between worker, machine, and en- 
vironment. Hazard analysis has not been 
used extensively by the mining industry, 
but it is being investigated by the Bu- 
reau for its potential benefits (18) . In 
the case of analysis of pneumatic coal 
haulage, the benefits of using hazard 
analysis are obvious because there are no 
actual accident statistics upon which to 
perform safety analyses; i.e., hazard 
analyses are the only possibilities, 

SHUTTLE CARS 

In the United States, shuttle cars are 
the most widely used means for transport- 
ing underground coal from a continuous- 
mining machine or loader to the central 
loading dump. The factors that make them 
so popular are as follows: 



Shuttle cars are usually long, low, 
self-propelled vehicles that receive cut 
coal or rock from the continuous-mining 
machine or loading machine and move it 
into the body of the car by means of a 
chain conveyor. The operator, seated at 
the side of the vehicle, controls the 
speed of the chain so that the coal is 
evenly distributed in the body of the 
car. When the car is full, the operator 
drives it back through the entries and 
crosscuts by a predetermined route to 
dump it at a loading site or onto a belt 
conveyor, using the chain conveyor in the 
car. Shuttle cars are designed to move 
forward or backward with ease, the only 
change involved is the direction that the 
operator faces. Consequently, the cars 
do not need to turn 180° while loading 
and unloading, which eliminates a poten- 
tial hazard. 

Shuttle cars are powered by diesel, 
batteries, or trailing electrical cables. 
Although electrically powered cars do 
not cause air pollution or have battery- 
related problems , the cables are suscep- 
tible to damage (run over by equipment or 
snagged on rock, for example) and present 
the potential danger for fires and injury 
to personnel (electrical shock and injury 
from whipping cables). Even so, cables 
are the most widely used source of power 
for underground shuttle cars. 



1. Flexibility, — Shuttle cars can 
adapt to almost any mining pattern, 
grade, pillar size, crosscut angle, or 
(within reason) entry width, 

2. Cost. — Shuttle cars are relatively 
inexpensive, with a wide variety of de- 
signs available. 

3. Reliability. — Individual units on 
production and standby can be selected 
for maximum uninterrupted production if 
maintenance is part of the plan. 

4. Mobility. — Shuttle cars move with 
the continuous-mining machine, so that 
when it is time to bolt or relocate, the 
transport system does not interfere. 



Trailing-cable shuttle cars are usual- 
ly used in pairs on a continuous-mining- 
machine section. It is nearly impossible 
to use more than two because of the ne- 
cessity of keeping their paths as sepa- 
rate as possible so that trailing cables 
do not become entangled. However, even 
using two shuttles, time delays due to 
changeouts often reduce the efficiency of 
the mining machine by making it wait for 
a car to load. This problem has been 
alleviated in some mines by using large- 
capacity belt feeders, enabling the cars 
to discharge their coal rapidly, and 
return to the mining machine quickly. 
Another solution has been to have the 
mining machine dump the cut coal direct- 
ly onto the floor where a gathering-arm 



I 



loader scoops it up to load shuttle cars 
as they become available. This arrange- 
ment leaves the mining machine free to 
work at full capacity but adds the capi- 
tal expense of an extra piece of equip- 
ment. Where diesel or battery-powered 
shuttles are used, more than two may 
be used on a section if ventilation is 
adequate. 

Shuttle cars are dangerous. They are 
almost constantly in motion, covering 
about 50 times the distance a continuous- 
haulage system would in a shift, often at 



relatively high speeds. This presents a 
very real hazard to those working on or 
around them. From 1978 to 1980, there 
were 2,357 accidents attributable to un- 
derground shuttle cars, accounting for a 
total of 61,742 lost workdays and 80,150 
statutory days charged. More than half 
of the accidents (1,254) involved injury 
to the car operator; the remaining vic- 
tims were engaged in such activities as 
getting on or off the machine, perform- 
ing maintenance, hand-shoveling, setting 
brattice, walking, etc. Table 1 presents 
an analysis of shuttle car accidents. 



TABLE 1. - Analysis of shuttle car accidents 



Type of accident and activity 
at time of accident 



Number of 
accidents 



Total days 
charged 



Fatalities 



Relative 
riski 



Caught — 

In collapsing materials , 

In meshing obj ects 

Between moving and stationary objects: 

Cleaning up , 

Coupling mine cars 

Electrical maintenance , 

Getting on or off equipment , 

Handling coal, supplies, timber...., 

Machine maintenance , 

Moving power cable. , 

Operating shuttle car 

Walking or running , 

Miscellaneous 

Between two moving 
objects: Miscellaneous , 

Not elsewhere classified: 

Handling coal, supplies, timber...., 

Machine maintenance , 

Operating shuttle car , 

Walking or running , 

Miscellaneous , 

Total , 

Struck by — 

Flying object: 

Moving equipment , 

Operating shuttle car , 

Miscellaneous , 

Falling object: 

Cleaning up 

Handling coal, supplies, timber..... 

Inspecting machinery , 

Machine maintenance , 

Operating shuttle car , 

Setting props ...., 

Miscellaneous , 



2 
4 

3 

3 

3 

10 

25 

19 

12 

174 

14 

43 

8 

32 
13 
47 
3 
23 



438 



1 
56 
34 

2 
31 

3 

57 

156 

1 
49 



106 
187 

6,295 

1,067 

289 

345 

758 

799 

607 

20,202 

4,855 

8,574 

133 

580 
667 
1,084 
120 
567 



47,235 



6,000 
411 
333 

6,001 

745 

1,010 

1,430 

3,657 

232 

565 



0.2 
.4 

13.3 

2.3 

.6 

.7 

1.6 

1.7 

1.3 

42.8 

10.3 

18.1 

.3 

1.2 
1.4 
2.3 
.3 
1.2 



33.2 



10.4 
.7 
.6 

10.4 
1.3 
1.8 
2.5 
6.3 
.4 
.9 



See explanation on page 10. 



TABLE 1. - Analysis of shuttle car accidents — Continued 



Type of accident and activity 
at time of accident 



Number of 
accidents 



Total days 
charged 



Fatalities 



Relative 
risk ' 



Struck by — Continued 

Sliding object: 

Electrical maintenance 

Operating shuttle car , 

Miscellaneous , 

Powered object: 

Getting on or off equipment...., 

Handling coal or supplies , 

Operating shuttle , 

Moving power cable. , 

Walking or running 

Miscellaneous 

Objects , n.e.c. : ^ 

Handling supplies or timber..,,, 

Idle , 

Machine maintenance , 

Moving power cable , 

Operating shuttle car , 

Walking or running , 

Miscellaneous , 

Total , 

Struck against — 

Moving object: 

Operating shuttle car , 

Operating mining machine , 

Miscellaneous , 

Stationary object: 

Escaping hazard , 

Getting on or off equipment,,,., 
Handling coal, supplies, timber, 

Machine maintenance , 

Operating shuttle car , 

Walking or running , 

Miscellaneous , 

Total , 



Electrical shock , 

Overexertion: 

Handle coal or supplies, timber, 

Machine maintenance , 

Operating shuttle car , 

Miscellaneous , , , , , 

Total , 



Falls 

Burns, heat, cold. 

Poisons , . , . 

Miscellaneous . . . . , 



1 

14 
17 

3 

9 

13 

8 

10 
54 

13 
8 
18 
8 
54 
12 
25 



657 



511 

4 

20 

3 
22 
15 
19 
140 
16 
13 



763 



28 

84 
41 
25 
50 



200 



144 
51 
16 
60 



6,000 
538 
288 

178 
494 
364 
254 
18,383 
1,506 

335 
516 
283 
225 
6,979 
693 
255 



57,675 



14,116 
533 
266 

333 
574 
314 
131 
3,166 
110 
132 



19,675 



6,495 

2,800 

1,298 

473 

1,465 



6,036 



3,888 
459 
144 
896 



10.4 
.9 
.5 

.3 
.9 
.6 
,4 
31,9 
2,6 

.6 
.9 
.5 
.4 
12.1 
1.2 
.5 



40.5 



71.7 
2.7 
1.4 

1.7 

2.9 

1.6 

.7 

16.1 

.6 

.6 



13.8 



4.6 

47.6 

21.4 

7.2 

23.8 



4.6 



2.7 
,3 
,1 
,6 



See explanation on page 10, "^Not elsewhere classified. 



10 



The term "risk," as used here, is a 
value calculated as the sum of the conse- 
quences times the probability of occur- 
rence. In other words, lost time is used 
as a severity factor, which includes ac- 
tual days lost, statutory days charged, 
and 0.5 times the number of restricted 
workdays. This measure of severity, or 
consequence, is then multiplied by the 
statistical probability of a type of ac- 
cident occurring, which results in the 
"relative risk." By using a probability, 
more weight can be given to those groups 
that occur more commonly, while statisti- 
cally rare events are normalized to some 
extent. Probability also converts these 
figures into relative values, providing a 
way to compare one to another within any 
specific group. 

The value of using risk becomes more 
apparent when inspecting the accident 
categories themselves. For example, in 
the first category in table 1 "caught," 
specifically "caught between moving and 
stationary objects," three separate cate- 
gories show that only three accidents 
occurred. These are for the activities 
of cleaning up, coupling mine cars, and 
electrical maintenance. The risk values 
are 13.3, 2.3, and 0.6, respectively, in- 
dicating major differences in the sever- 
ity of those accidents. By using risk as 
a measure, it is perhaps possible to come 
closer to the true interaction among ac- 
cidents in any category. 

Causes for these accidents range from 
faulty cable reels and damaged cables to 
poor visibility for the operator. In ad- 
dition, the car must travel through brat- 
tice curtains, creating potential hazards 
to unwary miners on the other side. Soft 
bottom, due to the cars driving continu- 
ously over the soft floor, leaves ruts 
and potholes that throw the operator 
around, causing injury to drivers, to 
operators of other nearby vehicles such 
as roof bolters or material supply cars, 
or to miners working in the area. 

A hazard analysis of a two-car shuttle 
haulage system is shown in table 2. This 
table shows the potentially hazardous 



conditions inherent in shuttle car haul- 
age, and the significance of potential 
accidents resulting from them. It also 
lists possible prevention or control mea- 
sures that should be taken. 

CONVEYORS 

Most underground coal mines use con- 
veyors (1) to off-load a longwall face, 
(2) from a production section to a cen- 
tral dump, or (3) as main haulage out of 
the mine. Attempts at using conveyors to 
off-load a continuous-mining machine have 
generally been unsuccessful because min- 
ing machines must move from entry to en- 
try and must cut crosscuts connecting 
them. Joy Manufacturing Co. developed 
an extensible belt that was useful in 
straight-line single entries or in reduc- 
ing tramming distance of shuttle cars, 
but could not handle multientry sections. 
Lee Norse Co. developed an extensible 
belt system that used crawlers to support 
the head and tail sections, with pairs 
of tram cars that could reach into the 
crosscuts. This system was not success- 
ful because of recurring mechanical prob- 
lems and the long time required to set up 
the equipment. In addition, it cost more 
than a shuttle car system used under the 
same conditions. Joy Manufacturing Co. 
designed a Serpentex conveyor that nego- 
tiates corners; however, it hangs by mon- 
orail from the roof, requiring more space 
than may be available in the entry. 
Thin-to-medium coal seams present partic- 
ular problems for conveyors because they 
do not provide the space required to 
operate such systems. 

Flat-link chain bridge conveyors have 
been used most successfully as face con- 
veyors in thin seams . They are capable 
of handling up to 8 ton/min, the esti- 
mated peak output of a continuous-mining 
machine operating in a thin seam, and 
have a maximum height of 30 in. Bridge 
conveyors take time to maneuver from en- 
try to entry, but they still operate 
within the time it takes for shuttle 
cars to change out. They are restricted 
most by their limited reach. Usually, 
only three entries with angled crosscuts. 



11 



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consisting of five working areas, may 
be worked from the center entry. At a 
(1981) total cost of $250,000, this is 
also more expensive than a shuttle car 
system. Meyercheck ( 19 ) gives a good 
summary of other developments in this 
area. 

Conveyors have drawbacks other than 
limited ability to handle face haulage. 
They have difficulty negotiating grades 
of over 30 pet (also a problem with shut- 
tles) , and are nearly useless when the 
entry or drift has many turns or bends. 
They take up a lot of room, and they are 
usually one-way systems. Unless specifi- 
cally designed to operate in reverse, a 
separate system must be used to bring 
supplies or materials into the mines. 

Conveyors are also dangerous. Most 
conveyors are open, which leaves miners 
who must work around them rather vulner- 
able. In the 3 years from 1978 to 1980, 
there were 1,970 accidents in underground 
coal mines related to conveyors. Table 3 
lists conveyor accidents by type of acci- 
dent and activity at time of accident. 
This table shows all the accidents dis- 
tributed into three levels: major type 
(e.g., caught), specific type (e.g., 
caught in meshing objects), and activ- 
ity. Again, the risk percentages for ma- 
jor types are relative to all underground 
conveyor accidents in coal mines, while 
the risk figures for subsequent levels 
are relative to that major type only. In 
the "caught" category, then, the risk 
values shown make up 100 pet of the 54.2 
pet relative risk attributed to "caught" 
type accidents. 

It is apparent from reading table 3 
that the main types of conveyor-related 
accidents are those in which miners are 
caught in the apparatus , or they are 
struck by some component of it or by the 
material conveyed. It would be valu- 
able to make a comparison between acci- 
dent per ton conveyed by conveyors and 
by other types of equipment. Unfortu- 
nately, the necessary data are not avail- 
able. It would be impossible, based upon 
the accident data alone, to rank the 
haulage systems commonly used according 



to their relative safety. Even so, con- 
veyors were involved in 1,970 accidents 
for the stated time period which, by 
itself, is enough to indicate a need to 
improve their safety record. 

The conclusion that can be drawn from 
these statistics is that it is dangerous 
to work on, or anywhere near, a convey- 
or. Because they are almost constantly 
in motion, are ubiquitous in the mine 
environment, and are largely unguarded, 
they present a constant opportunity for 
injury. 

SKIP HOISTING 

Skip hoisting in U.S. coal mines is 
limited, generally, to deep underground 
mines with vertical shafts. For haulage 
purposes, two skips are usually operated 
in counterbalance, with an electric hoist 
to raise and lower them. This leaves an 
empty skip at the underground loading 
site when the other is unloading on the 
surface. Skips may be loaded at the top 
and discharged through a gate at the bot- 
tom, or may be of the type that unloads 
through the top by rolling over. Shaft 
depth and hourly output are used to cal- 
culate the winding cycle and acceleration 
and deceleration rates. Cable strength 
and allowable stress are also calculated 
according to specific needs. 

Hoisting may be automated so that sig- 
nals will activate the hoist when the 
lower skip is filled and the upper one 
unloaded, or it may be manually activated 
by the hoist operator, reacting to a sys- 
tem of signals from the skip tender. Al- 
though hoisting may be automatic in this 
operation, it is required that a certi- 
fied hoist operator be present whenever 
the hoist is running. 

The inclusion of skip hoisting in a 
discussion on coal haulage systems may 
be somewhat misleading because there are 
several major differences between skip 
haulage and the other methods mentioned. 
Skip haulage is main haulage only and 
does not include face haulage as do shut- 
tles and some conveyor systems. One of 
the face haulage systems would have to 



13 



TABLE 3. - Analysis of conveyor accidents 



Type of accident and activity at time of accident 



Number of 
accidents 



Total days 
charged 



Fatalities 



Relative risk 



Caught — 

In meshing objects: 

Cleaning up 

Inspecting machinery 

Machine maintenance 

Other 

Between moving and stationary object: 

Machine maintenance 

Moving equipment 

Operating conveyor 

Riding equipment 

Other 

Between two moving objects: Miscellaneous activities.- 
In objects n.e.c.:^ 

Handling supplies , timbers , etc 

Machine maintenance 

Operating conveyor 

Other 

Total 

Struck against — 
Stationary object: 

Cleaning up 

Crawling , kneeling , walking 

Crossing over conveyor 

Getting on or off equipment , 

Hand loading , 

Handling supplies and coal timber 

Inspecting machinery , 

Machine maintenance 

Operating conveyor 

Riding equipment < 

Other , 

Moving object: 

Crossing over conveyor , 

Getting on or off equipment , 

Riding equipment , 

Using hand tools 

Walking or running , 

Other , 

Total , 

Overexertion: 
Lifting: 

Handling coal, rock , 

Handling supplies or timber , 

Machine maintenance , 

Moving equipment , 

Moving power cable , 

Other , 

Pushing or pulling: 

Handling coal or rock 

Handling supplies or timber 

Machine maintenance 

Moving equipment 

Moving power cable 

Other 

Wielding or throwing: 

Hand loading or cleaning up 

Other 

Overexertion, n.e.c: 

Crossing over conveyor 

Getting on or off equipment , 

Hand loading or clean up 

Handling supplies or coal 

Machine maintenance 

Moving equipment 

Using hand tools 

Other , 

Total 

'See explanation on page 10. ^uq^ elsewhere classified, 



5 

1 

8 

18 

17 
20 
14 
4 
55 
28 

55 
44 
11 
69 



349 



225 



4,897 

3,114 

12,079 

400 

6,517 
7,870 
1,010 
6,212 
2,871 
929 

1,362 
2,509 
1,264 
2,062 



53,096 



4,284 



15 


125 





25 


473 





21 


498 





10 


208 





14 


234 





28 


316 





1 


264 





32 


475 





5 


258 





19 


570 





23 


267 





3 


40 





3 


60 





4 


115 





1 


79 





1 


61 





20 


241 






22 


882 





05 


3,672 





40 


1,036 





51 


1,114 





1 


218 





10 


92 





5 


378 





23 


790 





30 


937 





19 


744 





3 


166 





5 


62 





3 


136 





5 


119 





10 


304 





9 


182 





22 


561 





36 


817 





26 


809 





14 


251 





4 


159 





13 


124 






9.2 

5.9 

22.8 

.8 

12.3 

14.8 

1.9 

11.7 

5.3 

1.8 

2.6 
4.7 
2.4 
3.8 



54.2 



2.9 

11.0 

11.6 

4.9 

5.5 

7.4 

6.2 

11.1 

6.0 

13.3 

6.2 

.9 
1.4 

2.7 
1.8 
1.4 
5.7 



4.4 



6.5 
27.1 
7.6 
8.2 
1.6 
.7 

2.8 
5.8 
6.9 
5.5 
1.2 
.5 

1.0 
.9 

2.2 
1.3 
4.1 
6.0 
6.0 
1.9 
1.2 
1.0 



456 



13,553 



13.8 



14 



TABLE 3. - Analysis of conveyor accidents — Continued 



Type of accident and activity at time of accident 



Number of 


Total days 


Fatalities 


Relative risk' 


accidents 


charged 






16 


274 





1.6 


50 


691 





4.0 


36 


882 





5.2 


18 


2,521 





14.9 


5 


308 





1.8 


15 


220 





1.3 


2 


6,000 


1 


35.5 


4 


211 





1.2 


31 


442 





2.9 


13 


236 





1.4 


11 


181 





1.1 


53 


691 





4.0 


32 


793 





4.7 


31 


556 





3.3 


26 


740 





4.4 


21 


193 





1.1 


11 


259 





1.5 


34 


511 





3.0 


3 


444 





2.6 


26 


385 





2.3 


18 


370 





2.2 


456 


16,908 


1 


17.2 


12 


196 





2.1 


21 


499 





5.3 


8 


214 





2.3 


11 


393 





4.1 


13 


565 





5.9 


3 


126 





1.3 


14 


348 





3.7 


31 


725 





7.6 


28 


538 





5.6 


28 


725 





7.6 


24 


734 





7.7 


5 


174 





1.8 


11 


213 





2.2 


12 


408 





4.3 


3 


104 





1.1 


8 


114 





1.3 


7 


254 





2.7 


9 


244 





2.6 


4 


113 





1.2 


6 


295 





3.1 


14 


417 





4.4 


12 


364 





3.9 


2 


141 





1.5 


5 


267 





2.8 


2 


347 





3.7 


1 


116 





1.2 


9 


175 





1.9 


4 


126 





1.3 


13 


567 





5.8 


320 


9,502 





9.7 


20 


160 





.2 


6 


66 





.1 


138 


437 





.4 



Struck by — 

Falling object: 

Cleaning up 

Handling supplies, coal, timber, etc 

Machine maintenance , 

Moving equipment 

Idle or observing 

Operating conveyor 

Supervising 

Walking or running , 

Other 

Flying object: 

Handling supplies, coal timber, etc 

Hand loading or cleaning up 

Miscellaneous 

Objects , n.e.c. : ^ 

Hand loading or cleaning up 

Handling supplies, coal timber, etc ■ 

Machine maintenance , 

Moving equipment 

Operating conveyor 

Other , 

Powered object: 

Handling supplies , timber 

Other 

Sliding object: Miscellaneous activities 

Total , 

Falls: 

Against object: 

Cleaning up 

Crossing over conveyor 

Getting on or off equipment 

Hand loading 

Handling supplies, coal, timber, etc 

Inspecting machinery 

Machine maintenance 

Walking or running 

Other 

From machine: 

Crossing over conveyor 

Getting on or off equipment 

Handling supplies or coal 

Machine maintenance 

Riding equipment 

Walking or running 

Other 

To working surface: , 

Hand loading or cleaning up 

Handling supplies or coal 

Machine maintenance t 

Moving equipment 

Walking or running 

Other 

On same level: 

Getting on or off equipment 

Crossing over conveyor 

Handling supplies or coal 

Cleaning up 

Other 

From walkway: Miscellaneous activities 

Falls , n.e.c 

Total 

Heat or cold 

Electric shock 

Miscellaneous and other 

'See explanation on page 10. ^Not elsewhere classified, 



15 



be used in conjunction with skip haul- 
age. In addition, one of the primary 
uses of skips is for transportation of 
workers and materials into and out of 
the mine. The accident statistics, how- 
ever, do not differentiate between trans- 
portation and production haulage. Only 
generic skip-related accidents are ref- 
erenced. Without the production fig- 
ures, it is impossible to give a good 
estimate for accidents per ton of coal 
hauled. 

The actual number of accidents related 
to coal skip hoisting for 1978 to 1980 is 
very low. Only 168 accidents were re- 
corded, 124 of which were noninjury acci- 
dents. These accidents could have been 
caused by hazards such as brake failure, 
causing overwinding of the cable drum; 
failure of the cables due to corrosion or 
overstress, resulting in the skip drop- 
ping to the bottom of the shaft; and dis- 
tortion or displacement of the guides, 
causing collisions between one skip and 
another. Human-error accidents are most 
common, however, and generally involve 
slips or falls from ladders or walkways, 
overexertion while loading the skip, or 
getting parts of the body caught in mov- 
ing equipment or between moving equipment 
and the shaft wall. These accidents are 
not peculiar to shafts, and, since miners 
rarely ride in skips except when starting 
or leaving a shift or when performing 
maintenance on the skip, they are not 
considered to be a major safety problem. 
Although an accident analysis of skip 
hoisting gives little information, the 
hazard analysis found in table 4 lists 
possible causes and solutions for poten- 
tially dangerous situations. 

Available data on hoisting accidents 
indicate that skip safety, although al- 
ways a concern, is probably not as urgent 
a concern for the coal industry as shut- 
tle, conveyor, or rail safety. A more 
relevant factor, perhaps, is cost. Skips 
generally operate in vertical shafts, 
although some hoisting operations are 
used to pull cars or buckets up steep 
slopes. If the shafts or main haulage- 
ways are not in existence, they are 



extremely expensive and time-consuming to 
develop. Alternatives would be of major 
interest to mine operators. 

RAIL HAULAGE 

Rail cars are generally used to trans- 
port coal from a central loading area 
underground to the surface. These cars 
are pulled by a locomotive that is either 
diesel or electric. The electric locomo- 
tives can be either battery-powered or 
trolley-type, drawing power from a high- 
voltage cable overhead. In some cases, 
the cars may be "winched" up the slope by 
a rope hoist. Rail cars may be used to 
transport coal and waste out of the mine, 
bring supplies into the mine, or, if the 
distance covered is great, to transport 
miners to and from the working area. 

The use of rail transportation presents 
hazards in a mine. In the period from 
1978 to 1980, there were 1,804 accidents 
in underground coal mines associated with 
rail cars, tracks, or locomotives; 22 of 
which were fatalities. This is at least 
twice the number of fatalities for any of 
the other haulage systems discussed. A 
list of those accidents by type of acci- 
dent and activity at the time of the ac- 
cident is shown in table 5. 

When reading this table, two categories 
seem to represent the majority of the 
serious accidents: caught between moving 
and stationary objects while operat- 
ing the locomotive (six fatalities) ; and 
struck by or against an object while 
walking, running, or operating a locomo- 
tive. Again, there is no way to differ- 
entiate between accidents involving coal 
haulage, delivery of supplies, or per- 
sonnel transportation. The causes of 
these accidents are equally obscure. To- 
tally replacing rail haulage with pneu- 
matic haulage would not solve the prob- 
lem because a major haulage system would 
still be necessary to bring supplies, 
timber, equipment, etc., into the mine. 
Reduction of rail traffic for coal haul- 
age, however, would improve rail safety 
by minimizing the potential for such 
accidents. 



16 



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17 



TABLE 5. - Analysis of rail haulage accidents 



Type of accident and activity at time of accident 



Number of 
accidents 



Total days 
charged 



Fatalities 



Relative risk' 



Caught — 

Between moving and stationary object: 

Riding equipment 

Coupling mine cars 

Handling supplies, timber, etc 

Operating jitney 

Operating locomotive 

Reralllng equipment 

Walking or running 

Other 

Between two moving objects: 

Coupling mine cars 

Riding equipment 

Other 

In objects, n.e.c.:^ 

Coupling mine cars 

Machine maintenance 

Operating locomotive 

Reralllng equipment 

Other 

Total 

Struck by — 

Falling object: 

Handling supplies or material 

Operating locomotive 

Reralllng equipment 

Other 

Flying object: 

Operating locomotive 

Other 

Powered object: 

Coupling mine cars 

Handling timber or supplies 

Operating locomotive 

Walking or running 

Other 

Sliding object: 

Escaping hazard 

Operating locomotive 

Other 

Objects , n.e.c. : 

Coupling mine cars 

Handling supplies , timber, etc 

Operating locomotive 

Reralllng equipment 

Riding equipment 

Walking or running 

Other 

Total 

Poisons: 

Inhalation of toxics (methane) 

Absorption of toxics 

Total 

Struck against — 
Stationary object: 

Coupling mine cars 

Getting on or off equipment 

Handling timber, supplies, etc 

Operating locomotive 

Operating or riding mantrip 

Reralllng equipment 

Riding equipment 

Other 

'See explanation on page 10. 2[}ot elsewhere classified. 



14 
52 
29 

1 
43 
19 

4 
42 

17 
3 

14 

45 
5 
23 
26 
80 



417 



19 
50 
10 
25 

24 
18 

12 
5 
9 
5 

23 

1 

4 
14 

13 
9 

46 

15 
8 
1 

36 



347 



5 
11 



16 



482 
2,932 

741 
6,000 
51,222 
7,778 
6,440 
1,554 

1,289 

6,055 

730 

959 

554 

659 

7,017 

1,318 



95,730 



517 
754 
325 
573 

281 
185 

325 

303 

597 

6,075 

5,302 

3,000 
6,220 
6,221 

204 
424 
897 

1,599 
630 

6,000 
426 



40,858 



30,000 
26 



30,026 



11 



10 


138 





55 


1,435 





17 


359 





96 


2,838 





7 


189 





17 


338 





29 


669 





32 


375 






0.5 
3.1 
.8 
6.3 
53.5 
8.1 
6.7 
1.6 

1.3 

6.3 

.8 

1.0 

.6 

.7 

7.3 

1.4 



42.4 



1.3 

1.8 

.8 

1.1 

.7 
.4 

.8 

.7 

1.5 

14.9 

12.9 

7.3 
15.2 
15.3 

.5 

.9 

2.2 

3.9 

1.5 

14.7 
1.6 



18.1 



99.0 
1.0 



13.3 



.5 

5.6 

1.4 

11.0 

.7 
1.3 
2.6 
1.5 



18 



TABLE 5. - Analysis of rail haulage accidents — Continued 



Type of accident and activity at time of accident 



Number of 


Total days 


Fatalities 


Relative risk' 


accidents 


charged 






2 


184 





0.7 


125 


17,334 


1 


67.1 


18 


392 





1.5 


31 


1,229 





4.8 


28 


355 





1.3 


467 


25,835 


1 


11.5 


12 


279 





2.2 


5 


338 





2.7 


A 


12,081 





95.1 


21 


12,698 





5.6 


4 


103 





1.4 


13 


178 





2.3 


15 


362 





4.8 


1 


75 





1.0 


1 


83 





1.1 


7 


63 





.8 


3 


93 





1.2 


12 


328 





4.3 


10 


180 





2.4 


44 


1,255 





16.5 


66 


2,123 





27.9 


2 


58 





.8 


17 


668 





8.8 


3 


686 





9.0 


9 


248 





3.3 


13 


347 





4.5 


3 


152 





2.0 


1 


97 





1.3 


1 


58 





.8 


4 


60 





.8 


5 


29 





.3 


3 


30 





.4 


1 


110 





1.4 


3 


100 





1.3 


3 


19 





.3 


2 


93 





1.2 


I 


6 





.1 


247 


7,604 





3.4 


20 


6,340 


1 


2.8 


47 


1,559 





27.7 


28 


907 





16.1 


1 


19 





.3 


75 


3,154 





55.9 


151 


5,639 





2.5 


80 


960 





.4 


38 








.0 



Struck against — Continued 
Moving object: 

Getting on or off equipment.... 

Operating locomotive 

Operating or riding mantrip.... 

Riding equipment 

Other 

Total 

Miscellaneous accidents: 

Bodily reaction 

Insufficient data 

Accidents, n.e.c.^ 

Total 

Falls: 

Against object: 

Escaping hazard 

Getting on or off equipment.... 

Handling timber, supplies, etc. 

Moving equipment 

Operating j itney 

Operating locomotive 

Reraillng equipment 

Walking or running 

Other 

From machine: 

Escaping hazard 

Getting on or off equipment.... 

Machine maintenance 

Operating locomotive 

Operating or ride mantrip 

Riding equipment 

Other 

On same level: 

Handling timber, supplies, etc. 

Operating rockdust machine 

Rerailing equipment 

Walking or running 

Other 

To working surface: 

Handling supplies or material.. 

Rerailing equipment 

Walking or running 

Other 

Falls , n.e.c. : 

Getting on or off equipment.... 

Rerailing equipment 

Total 

Electric shock 

Overexertion: 

Lifting 

Pushing-pulling 

Wielding, throwing 

Other, n.e.c 

Total 

Burns, heat, cold 

Other 



'See explanation on page 10. ^Not elsewhere classified. 



19 




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20 



The rail hazard analysis shovm in ta- 
ble 6 presents potential dangers for a 
rail transportation system used to off- 
load a tunnel-boring machine driving a 
12-ft-diam tunnel into a coal seam. This 
is a specific application of rail haulage 
that excludes rail transportation used 
for supplies, workers, or materials. Al- 
though it may be difficult to make a fair 
comparison of hazards between this type 
of rail haulage and other conventional 
haulage systems, this situation was 



imposed to better compare rail haulage 
with pneumatic haulage used in the same 
tunnel-driving application. The hypothe- 
tical tunnel under development is being 
driven at a near-level grade, but it does 
contain bends that obstruct vision. Be- 
cause of limited space, only one set of 
tracks is installed, with a passby out- 
side the tunnel entrance to allow two 
sets of locomotives and rail cars to 
operate. 



SAFETY AND HAZARD ANALYSIS OF PNEUMATIC TRANSPORT 



Pneumatics has not been used in this 
country to transport coal from the face 
or section to the secondary haulage sys- 
tem, nor, to any great extent, has it 
been used to transport coal out of the 
mine. As British and European mining 
companies have discovered, there are ad- 
vantages to the application of pneumatics 
for this type of haulage. The Colorado 
School of Mines (20) listed the benefits 
as follows: 



1. Elimination 
conveying. 



of 



straight-line 



2. One system capable of serving many 
feeder or discharge points. 

3. Elimination of dust. 



4. Low 
waste) . 



handling losses (minimum 



5. Cleanliness and operational safety. 

Some of the disadvantages listed in the 
same report were as follows: 

1. High capital cost. 

2. High power cost. 

3. System is one-directional. 

This section will be concerned with the 
safety aspects of pneumatics rather than 
the logistical ones. The hazards dis- 
cussed will be fires and explosions 
(which are probably the primary concerns 
of safety experts in the United States) , 
dust, and noise. Results of several 



research studies addressing these issues 
have been well-documented. 

The emphasis on pneumatic safety re- 
search in the United States has been 
on the danger of explosion within the 
system should a volatile mixture of air 
and methane ignite coal or coal dust 
in transport. Possible sources of igni- 
tion include sparking by rock or tramp 
iron being conveyed by the system; coal, 
heated by an external force, entering 
the systems; or spontaneous combustion of 
coal or gases trapped within the system 
during extended idle periods. 

Fires and explosions were the subjects 
of a Bureau research project in 1976. 
Kelly and Forkner (21) state that "coal 
dust in air alone is not ignited by abra- 
sive impact, but additions of as little 
as one volume percent methane to the coal 
dust air mixture resulted in ignitions. 
However, results of single-impact tests 
indicate that ignition of such a mixture, 
or of air and methane, is very unlikely 
from the type of low-angle glancing im- 
pact that tramp rock or metal would make 
in a coal-carrying pipeline." Another 
study by Soo and Pan ( 22 ) stated that 
even though coal dust particles below 20 
ym could be ignited in a tube with a 1:1 
mass ratio, the flame was smothered by 
coarser particles. Since the pneumatic 
system proposed in the study handled coal 
smaller than 0.25 in, with a 10:1 coal- 
to-air mass ratio, they concluded that 
such a pneumatic system was actually 
safer than conventional systems. Michael 
Rieber (23) prepared an analysis of pneu- 
matic conveying for the National Science 



21 



Foundation in 1975 and came to much the 
same conclusion, stating that the possi- 
bility of an explosion in the pipeline 
during operation was remote because of 
the high velocity of transport. In ef- 
fect, any flame or spark within the pneu- 
matic system would be smothered, even if 
deliberately introduced. 

Only one published study reports high 
potential fire and explosion hazards in 
pneumatic transportation of coal. In a 
1978 Bureau report, Litchfield ( 24 ) con- 
cluded that this method of haulage was 
"...an accident waiting to happen." This 
paper, prepared for the Pneumo transport 
IV Conference in 1978, was never pre- 
sented because of the death of Litchfield 
shortly before the conference convened. 
His conclusions, however, were challenged 
at the conference. Archie Johnston, Di- 
rector of the Safety in Mines Research 
Establishment of Britain, stated that 
while the points made in the paper were 
valid, their relevance to actual situa- 
tions was questionable, and that it was 
highly unlikely that methane would col- 
lect in the system in quantities suffi- 
cient to present a real hazard ( 25 ) . 

J. E. Powell of Radmark Engineering, 
Inc. , discussed the same paper and stated 
that he had talked with Litchfield short- 
ly before his death and explained the ac- 
tual installation of a pneumatic hoisting 
system. Litchfield, he said, had no ob- 
jection to the use of pneumatics to hoist 
underground coal if the equipment were 
permanently installed and regularly in- 
spected, with the blower in the intake 
air split. He also felt safety and haz- 
ard tests should be conducted ( 26 ) . In 
regard to other pneumatics applications , 
off-loading a continuous -mining machine, 
for instance, Litchfield felt thorough 
investigations should be completed before 
approval was given. 

Ideally, hazards such as methane, dust, 
and sparking from tramp rock, etc. , 
should be eliminated from a pneumatic 
system, but that is not practical. The 
rapid movement of coal and rock through 
a pipe implies the presence of dust. 



methane, and sparks. Although precau- 
tions against explosions should be taken, 
including the suppression of any flame, 
the system should be designed to safely 
withstand such occurrences. The follow- 
ing precautions are suggested as possible 
solutions to minimize or eliminate the 
various hazards mentioned in relation to 
pneumatics. 

METHANE-AIR MIXTURE 

The blowers providing pressurized air 
to the pneumatic system should be located 
in fresh air, in an intake airway other 
than that used by the conveyor belt, rail 
entry, or the discharge unit. Discharged 
air should not be used for further venti- 
lation, but should be led directly to the 
return entry. Although it is inevitable 
that some methane would enter the system, 
a methane detector mounted at the intake 
filter would shut down the system if an 
explosive level were reached. Detectors 
would also check the conveying air deliv- 
ered to the blower, preventing the unit 
from starting up should high methane lev- 
els be discovered. 

With the blower located in an intake 
airway, the main source of methane con- 
tamination (the face) is eliminated. 
There is, however, a possibility of meth- 
ane building up within the pipeline, par- 
ticularly if the system is idle for 
extended periods , or if the pipeline con- 
tains a high spot, due to undulations in 
the entry, where methane would tend to 
accumulate. The pipeline system is, for 
the most part, closed to the mine atmos- 
phere when not in operation. There is 
still, however, some air circulation 
through the clearances in the blower, the 
rotor of the feeder, and through the 
pipeline, bringing in methane and thus 
introducing a danger of explosion at 
startup time. 

A small auxiliary blower located at the 
feeder could prevent a startup explosion. 
This blower, drawing air from the main 
airline, would be used to flush the pipe- 
line and both end housings to clear them 
of dust and any methane buildup. It 



22 



would also serve to pressurize the pock- 
ets so that the sudden in-rush of air 
when the conveying lines open does not 
momentarily suspend any material in the 
pocket. The air from the auxiliary blow- 
er would have the capacity to flush 
the system, yet would be of a velocity 
low enough not to disturb any ignition 
sources such as tramp iron that might 
have been trapped in the line during 
shutdown. Any methane or dust that has 
accumulated would be safely diluted be- 
fore the system started up, or the meth- 
ane detectors on the various components 
would not allow operation until the sys- 
tem is fully purged. 

At the time the main blower is acti- 
vated, there is a possibility that smol- 
dering coal dust, glowing coals, or tramp 
iron would be picked up and moved through 
the system. All traces of methane should 
have been removed by this time, how- 
ever, eliminating the danger of an inter- 
nal explosion. To prevent discharge of 
any incandescent materials into the at- 
mosphere, water sprays would be activated 
at three locations coincidental with the 
startup of the main blower: (1) at the 
blower, to assist in cooling the convey- 
ing air stream and in extinguishing any 
glowing coals or heated dust, (2) at the 
feeder, to reduce the likelihood of any 
dust that escapes the conveyor cowling 
from becoming airborne, and (3) at the 
discharge unit, to reduce airborne dust 
released into the atmosphere by the ex- 
hausted air. 

This procedure should be followed every 
time the system is started up, includ- 
ing after relocation of the feeder or 
addition of pipeline. To ensure that 
this is done, an electrical interlock 
could be installed between the starters 
on the auxiliary blower and the main 
blower, which would prevent operation 
unless the system has been completely 
purged. Using these precautions, any 
flame would be suppressed by the cooling 
effect of the pipeline, the water-satu- 
rated air, and the larger particles of 
coal traveling through the pipeline, 



which have a tendency to suppress the 
propagation of flames. 

Another precaution could be built into 
the system, especially in those appli- 
cations in which the conveying air would 
be exhausted into the mine atmosphere 
(conveying coal from the face to an 
underground central loading dump for in- 
stance). This would consist of an en- 
closed tank built into the roof of the 
discharge unit, which would hold a large 
amount of water. The level of water 
would be controlled by a float valve to 
ensure that a sufficient amount is avail- 
able at all times. An electrical inter- 
lock would prevent operation of the sys- 
tem unless the tank were full. This tank 
would be activated by the force of an 
explosion in the pipeline by means of 
hinged flaps fitted with rubber seals. 
The weight of the water would be suffi- 
cient to keep the flaps closed under nor- 
mal conditions, but any explosion within 
the system would lift the flaps, causing 
the water to cascade into the discharge 
unit, extinguishing any flames that might 
be present. The hot gases created by 
such an explosion would have to pass 
through the dust filter before being 
vented into mine air, which would further 
cool them. Depending upon where the ex- 
plosion takes place, the conveying air 
within the pipeline would reverse momen- 
tarily through the force of the blast, 
and, coming into contact with the cooler 
air from the blower, would dilute and 
quench the burning gases as they are 
swept into the discharge unit. 

By ensuring that all components of the 
system are strong enough to withstand an 
explosion, any such explosion could be 
allowed to take its full course. 

EXTERNAL COAL DUST 

External dust is always present in un- 
derground environments , and any discharge 
of pressurized air from the pneumatic 
system would cause a problem with air- 
borne dust. This could occur in several 
ways: 



23 



I 



I 



1. Pipe fracture. 

2. Pipe joints uncoupling. 

3. Air from the blower misdirected in- 
to a circuit not connected to the feeder 
unit. 

4. Elbow left open, 

5. Feeder not coupled. 

The following precautions should be taken 
to handle such occurrences: 

1. Pipes should be strong enough me- 
chanically to withstand minor roof falls 
and the normal wear and tear attributable 
to underground mining. For maximum pro- 
tection, they could be of double-wall 
construction with an annular space be- 
tween the inner and outer pipes. If 
the inner pipe should fracture or wear 
through, the annular space would be 
filled with pressurized air, activating a 
whistle-type alarm that would identify 
the affected pipe immediately so that it 
could be replaced. If both inner and 
outer pipes should break (in a major roof 
fall, for instance) , the water normally 
stored in the annular space would flow 
toward the break, saturating the escaping 
air and thoroughly wetting any dust in 
the area. The noise of air escaping the 
break and the wet area would alert any 
personnel in the vicinity, as would the 
drop in pressure at the feeder unit. The 
system would be shut down immediately. 

Pipe sections should be assembled on 
skids linked together at the base. This 
protects the pipe joints because it is 
the skids that are used to push and pull 
the pipeline into or back from a working 
place. In addition, the joints should be 
connected with wedge-shaped locks set in 
place with hydraulic cylinders, making it 
virtually impossible to become acciden- 
tally uncoupled. 

2. Pipe joints should be inspected 
regularly by a maintenance crew to ensure 
that they have not slacked off. 



3. A spring-loaded, air-pressure re- 
lief valve located in the manifold of 
the discharge unit would allow pressur- 
ized air from the blower to bypass the 
pipeline and vent through the discharge 
chamber to the atmosphere. Although the 
valve is normally set up to prevent 
the buildup of high pressure within the 
blower, it could also be opened by a 
hydraulic cylinder, activated by a pilot 
circuit which checks the pipeline and 
feeder. If the circuit is not complete 
because of improper coupling of the pipe- 
line, the air-pressure valve would open 
automatically, allowing the air to escape 
into the discharge chamber. This would 
prevent pressurized air from being routed 
through a partially open pipeline. 

4. Coupling and uncoupling of elbows 
should be done by the pipeline operator. 
If an elbow is not properly coupled, the 
escape of air would be noticeable, and 
the system would be shut down until a 
proper joint is made. Because the pilot 
circuit includes the feeder, and because 
of the presence of an indicator light 
showing the pipeline operator whether 
there is a complete circuit, it is doubt- 
ful that the system would be acciden- 
tally started up with the feeder unit 
unattached. 

STATIC ELECTRICITY 

A paper by Singh and Courtney ( 27 ) 
states, "the passage of relatively dry, 
high velocity, stony material through a 
steel pipe generates considerable static 
electricity, and witnessing a pneumatic 
stowing operation also implies seeing a 
stream of sparks. Although no known ex- 
plosions have occurred in coal mines that 
could be ascribed to this source, it can- 
not be ignored and deserves attention." 

The pneumatic conveying system is com- 
pletely interconnected mechanically, 
providing a solid ground for any static 
electricity that builds up in the 
pipeline. Also, the pilot circuit is 
grounded through the feeder, discharge 
unit, and blower. The blower unit is 



24 



grounded through the electrical cables 
that supply its power. In addition, the 
continuous spray of water used in the 
system will help eliminate static charge 
buildup and prevent the development of a 
dangerous situation. 

THERMITE REACTION 

There is always the possibility of ma- 
chine parts or other foreign metal enter- 
ing the system. This would be of partic- 
ular importance during startup after a 
long period of downtime during which some 
pipe or discharge components might have 
accumulated rust. Kelly and Forkner (21) 
conducted tests dealing with this prob- 
lem and reported that some sparking was 
observed, but there was no evidence of 
thermite reaction. A permanent magnet, 
however, located over the feeder conveyor 
to pick up any tramp iron before it en- 
tered the system would be an adequate 
deterrent. 

NOISE 

Sources of noise from a pneumatic con- 
veying system include the blower, pipes, 
feeder, and discharge unit. Of these, 
the main noise source is the blower. Al- 
though, generally, miners would not be 
working close to the blower, silencers on 
the intake and exhaust, and acoustic 
cladding around the blower and its motor, 
would bring the noise level within com- 
fortable limits. 

Nicholson ( 28 ) lists the following dec- 
ibel levels for a pneumatic system used 
for vertical hoisting. These readings 
were observed underground near the blow- 
er, feeder, and pipes. The blower was 
contained within a room constructed of 
sound-damping bricks rather than in an 
acoustically clad room. 

dB 

Adjacent to air blower Ill 

Within the blower room 104 

Immediately outside blower room. 94 



At air intake silencer 89 

At rotating airlock feeder 81 

Pipeline adjacent to feeder 86 

Pipeline as it enters mine shaft 81 

For comparison, the noise levels for 
several typical mining activities or ma- 
chines are listed below (29) . 

dB 

Loading machine 108 

Continuous-mining machine 107 

Shuttle cars 98 

Rotary drill 92 

Trucks 90 

Normal conversation 65 

Excepting the blower, noise emitting 
from the components of the pneumatic sys- 
tem is not considered a problem. The 
pipeline is no noisier than other machin- 
ery in the area and is, in fact, rela- 
tively quiet when actually transporting 
coal. At the discharge end of the sys- 
tem, the air goes into an enclosed unit 
where it is allowed to expand before en- 
tering the atmosphere. This provides 
little opportunity for extraneous noise 
due to airflow. The water tanks and sol- 
id sidewalls built into the discharge 
unit also prevent reverberation. 

The problems of noise, dust, and meth- 
ane are not unique to pneumatics; they 
are prevalent in most mine situations. 
Other forms of coal transport must also 
deal with friction or static sparking and 
with thermite reaction; however, any fire 
or explosion that might occur is not con- 
tained within the system, as it would be 
in a pneumatic system. Any pneumatic 
system must eventually be responsible for 
its unique safety needs, but the overrid- 
ing principle remains the same: The sys- 
tem should be designed to withstand and 



25 



contain such catastrophic occurrences as 
roof-falls, fires, or explosions. 

When discussing the safety of pneumatic 
haulage, one must consider that the 
system is designed to be relatively stat- 
ic. Consequently, miners are not exposed 
to continuously moving vehicles , which 
are a constant hazard to personnel. For 
the most part, it is an enclosed system, 
which minimizes the hazard of miners be- 
ing caught in or struck by the equipment. 
The elimination of potentially dangerous 
situations may be one of the most impor- 
tant safety aspects. 



Tables 7, 8, and 9 show hazard anal- 
yses for pneumatic systems to handle off- 
loading a continuous-mining machine, ver- 
tical hoisting through a shaft, and 
off-loading a tunnel-boring machine. 
Again, the analyses are relative to fair- 
ly specific applications of pneumatic 
haulage systems. These are certainly not 
the only applications possible, nor 
are they meant to represent mine haulage 
in general. Instead, they illustrate 
the versatility of pneumatic haulage 
and serve as a basis for comparison to 
the conventional systems previously 
discussed. 



PNEUMATIC ALTERNATIVES TO CONVENTIONAL HAULAGE 



One of the major advantages to the 
use of pneumatic conveying is its adapt- 
ability to widely varied haulage prob- 
lems and mine layouts. Three applica- 
tions that have been designed and tested 
are (1) off-loading a continuous-mining 
machine on a room-and-pillar section, 

(2) vertically hoisting coal through a 
shaft, and (3) off-loading a tunnel- 
boring machine. 

The basic equipment requirements for 
all three low-pressure, positive pneumat- 
ic haulage systems are the same: (1) a 
rotary airlock feeder for metering and 
feeding the pipeline, (2) a blower to 
provide the pressurized air necessary to 
convey the material through the pipeline, 

(3) a hydraulic power-pack control con- 
sole to operate and control the feed- 
ing system, (4) a thick-walled abrasion- 
resistant material-conveying pipeline, 
and (5) an air pipeline to supply pres- 
surized air from the blower to the con- 
veying pipeline. The individual systems 
each have other peripheral equipment spe- 
cific to their application. Each system 
and its requirements will be discussed in 
detail. 

OFF-LOADING A CONTINUOUS-MINING MACHINE 

Room-and-pillar mining requires mobile 
mining and haulage equipment in order 
to accommodate rapid face changes. 



Crosscuts must be negotiated, and when a 
sequence has been completed (that is, one 
pillar length and the crosscuts between 
entries driven) , section haulage equip- 
ment must be moved up one pillar length. 
The ratio feeder and panel belt, or rail 
track, must be moved quickly to minimize 
downtime. The equipment must be flexible 
enough to retreat rapidly during the re- 
covery stage of mining. It is crucial to 
the operation of the haulage system that 
it fit into the space available (seam 
thickness) and not interfere with mining, 
support, or supply operations. The Rad- 
mark Engineering, Inc. , pneumatic system, 
designed under contract to the Bureau of 
Mines and described below, met all of the 
criteria. 

This pneumatic system is designed to 
convey 10 tons of coal per minute up to 
600 ft to the section belt conveyor. 
Seam height is assumed at 48 in. The 
components of the system are a feeder 
combine, which includes a rotating air- 
lock feeder; an infeed conveyor and nec- 
essary peripheral equipment; the pipeline 
assemblies; the elbow assemblies; the 
discharge unit consisting of the expan- 
sion chamber, material pipeline mani- 
fold, feed-out chain conveyor, and power 
pack; and the blower, blower drive motor, 
starter inlet filter, and silencer. A 
detailed description of the equipment was 
reported by Powell (2). 



26 



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28 



A typical mine layout is shown in fig- 
ure 1, with seven entries 20 ft wide, 
and crosscuts and pillars on 100-ft cen- 
ters. One continuous-mining machine, 10 
ft wide and 30 ft long, is working the 
section. Several mining machines and 
feeder-combine units are shown in figure 
1, but this is merely to illustrate the 
variety of situations that can be handled 
by the pneumatic system. 

When in operation, the feeder-combine 
is attached directly to the mining ma- 
chine or loading machine through the in- 
feed of the receiving conveyor. The 
feeder, which is mounted on crawlers but 
remains stationary during operation, is 
fed coal continuously by the receiving 
conveyor, which extends along with the 
pipe telescopes to follow the miner. The 
rotating air-lock feeder moves the coal 
into the entry pipeline, through the el- 
bows to the crosscut or gathering pipe- 
line, and then to the blower-discharge 
unit. Here, the coal is discharged into 
an expansion chamber and picked up by a 



flight chain conveyor that moves it onto 
the panel-belt conveyor, into mine cars, 
or onto whatever haulage system is used 
to transport it out of the mine. The 
loading terminal, consisting of the dis- 
charge unit, blower, expansion chamber, 
feed-out conveyor, pipeline manifold, and 
power pack, is mounted on hydraulically 
powered crawlers or on a sled. As a min- 
ing sequence is completed, the whole unit 
is moved in a straight line down the belt 
entry by one pillar length to the next 
crosscut. 

The pipeline and elbow assemblies used 
to connect the feeder and discharge sta- 
tion are critical to the smooth operation 
of the system. Pipe sections are 20 ft 
long and are supported on skid bases. 
Pipes and joints are supported in cradles 
that allow them to rotate (reducing un- 
even wear), but straps are used to re- 
strain them from moving laterally. When 
the faces are in production, up to 10 
sections of pipe are needed for each en- 
try, and 5 for the crosscut pipeline. 




No, 1 



No. 2 



No. 3 



No. 4 



Continuous-mining machine 

Feeder-combine 

Pipe telescopes 

Entry pipeline 

Elbows 

Gathering pipeline 

Blower-discharge unit 

Gathering pipeline 

Bridging telescope pipe 

Bridging elbow 

Battery car 

Roof bolter 



FIGURE 1. - Pneumatic haulage on room-and-pillar section. 



29 



The pipeline is installed on the right- 
hand side of the entries, facing the work 
area. Bridging telescope sections and 
elbows are used to connect entry sections 
to the crosscut pipeline, usually with 
only one entry connected to the blower- 
discharge unit at a time. The skid bases 
for the pipeline are 5 ft wide, leaving 
ample room for vehicular travel, but the 
elbow assemblies take up much more space. 
When it is necessary for a vehicle to 
pass through a crosscut containing an el- 
bow assembly, the telescoping pipe sec- 
tions attached to the elbow are disen- 
gaged and retracted. 

After a mining sequence has been 
completed, with all crosscuts broken 
through, the crosscut pipeline is moved 
in sections to the next crosscut, and the 
pipelines and elbows are pulled forward 
using the hydraulic winches, or using the 
feeder-combine, a trailer, or a battery 
car. The crosscut, or gathering pipe- 
line, is always kept in the second cross- 
cut back, leaving the crosscut nearest 
the face open as a travelway for the min- 
ing machine, loader, bolter, and feeder- 
combine. When the gathering pipeline is 
repositioned and connected to the entry 
pipelines, and the blower-discharge unit 
has been moved forward, the system is 
again ready for operation. Because this 
can be accomplished in sections, as the 
separate entries advance, there is mini- 
mal downtime. As an entry is completed, 
that portion of the crosscut pipeline is 
simply disconnected and advanced, leaving 
the rest of the pipeline intact to ser- 
vice the entry currently being mined. 

There are many alternative possibil- 
ities to the use of this face haulage 



system. For example, the system de- 
scribed could easily be expanded to in- 
clude primary haulage out of the mine. 
This would be accomplished with either a 
separate system at a more central loca- 
tion, servicing all the working sections; 
or with a redesigning of this system, 
provided the distance to the surface dump 
was not excessive. 

Two full-time operators are required to 
operate this system: a pipeline operator 
to handle assembly and disassembly of 
elbows and pipes and inspect the pipeline 
for leaks or faulty joints; and a feeder- 
combine operator to handle the electrical 
and hydraulic controls and steer the ma- 
chine as it follows the continuous-mining 
machine into a new entry or crosscut, A 
battery-scoop operator (or an equivalent 
worker) is also required on an intermit- 
tant basis when it is time to move the 
crosscut pipeline. 

The system, as designed, requires 
10,000 cfm of air at the inlet of the 
blower, pressurized to 18 psi, to move 
the required tonnage a maximum of 600 ft. 
To accomplish this, two blowers, oper- 
ating in parallel, each producing one- 
half of the necessary quantity of air, 
would be used. Each would be rated at 
400 hp, operating at 1,900 rpm. The 
material-conveying pipeline would be 
double-walled. The interior pipe has a 
20-in CD, 0,375 in thick, and the exte- 
rior has a 20-in ID, with 0,188-in walls. 
The air pipeline is a 20-in-OD pipe with 
0.188-in walls. The estimated cost of a 
system such as the one described (in 1981 
dollars) is presented in the following 
tabulation: 



Blower-discharge unit: 

Crawlers and safety devices $250,000 

Feeder combine including air-lock feeder, 

chain conveyor, operator's cab, and crawlers,,, 200,000 

Air- and material-conveying pipeline (2,000 ft) .,, 200,000 

Six elbow assemblies 120,000 

Total 770, 000 



30 



For comparison, the estimated cost of a 
shuttle car setup for the same section is 
shown in the tabulation that follows: 

Two 5.5-ton~capacity cable 
reel shuttle cars, includ- 
ing 700 ft of trailing 
cable each $200,000 

One ratio feeder 120,000 

Total 320,000 

VERTICAL HOISTING 

The vertical hoisting application is 
designed to lift 4,400 tons per day a 
distance of 1,200 vertical ft. Delivery 
of material must average 3.33 ton/min, 20 
pet of which is assumed to be waste rock. 
Equipment must be designed to accommodate 
large intermittent loads, or a bunker 
must be installed to level out the peaks. 
Since the bunker is much more economical 



than an overdesigned system, a 50-ton- 
capacity bunker is included in this sys- 
tem. Figure 2 shows a potential layout 
for such a pneumatic hoisting system. 
The pneumatic equipment is similar to 
that used for the face haulage applica- 
tion; that is, it consists basically of a 
feeder, blower, pipeline, and discharge 
station. The main difference in the 
hoisting system is the addition of the 
storage bunker. 

The bunker includes a heavy-duty chain 
conveyor running its length, with a vari- 
able-speed hydraulic motor. The bunker 
has sloping sides and holds approximately 
1 ton of coal per running foot. A feeder 
conveyor from the sections is located 
above the bunker (fig. 2), discharging at 
the front end, where the coal is picked 
up by a second conveyor that carries 
it through the breaker to the feeder. 



50- 



Cyclone 



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Blower room 



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I 



Control room 



18-in-OD pi; 



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50-ton bunker conveyor 



FIGURE 2. - Feeder, breaker, and bunker conveyor for vertical hoisting. 



31 



Near the coal pile created by the feeder 
conveyor are electronic sensors that 
activate the bunker conveyor when more 
coal is received than is going out to 
the feeder. The bunker conveyor moves 
approximately 12 in before automatically 
shutting off. When the coal pile again 
reaches the set limit, the conveyor 
switches on, moving another 12 in, thus 
eventually filling the bunker in incre- 
ments. When the bunker is full, the 
feeder belt is shut down, A coal stock- 
pile is thus created so that if produc- 
tion is unusually high, or if the pneu- 
matic hoisting apparatus is temporarily 
shut down, mining is not disrupted. 

When coal is contained in the bunker, 
and none is being conveyed from the face, 
a second sensor switch reverses the 
bunker conveyor, which begins feeding the 
stored coal onto the transfer belt. The 
two sensors, working together, act to 
effectively regulate the coal entering 
the haulage system, thus ensuring an even 
flow out of the mine. This operation is 
coiiq)letely automatic, although there are 
manual overrides. If there is no coal 
available for transport, the pneumatic 



hoisting equipment shuts off and auto- 
matically restarts when coal delivery 
resumes. 

After leaving the breaker, material 
is fed into the rotating air-lock feeder 
set 30 ft from the shaft bottom where 
it traverses through a 90° elbow, up 
1,200 ft of vertical pipe, through anoth- 
er 90° elbow, and out 50 ft or so to 
the discharge cyclone where the air is 
vented. The coal is then picked up by a 
conveyor belt and transported to the 
cleaning plant. 

Figure 3 shows the layout plan for the 
blower assembly located approximately 200 
ft from the feeder unit. Silencers are 
placed at the intake and discharge of the 
blower assembly to minimize noise. 

The amount of air necessary to lift the 
desired quantity of coal vertically 1,200 
ft is calculated to be 19,960 cfm, pres- 
surized to 15 psi. Two blowers are used, 
operating in series , with each producing 
half the pressure needed. They operate 
at 880 rpm and are driven by a 800-hp 
electric motor. 



Ventilation — »- — *- 



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Hydraulic power pack 
Control room 




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Main conveyor 



FIGURE 3. - Layout plan for pneumatic vertical hoisting. 




L 



32 



The feeder requires a separate 32-rpm 
hydraulic motor powered by a 30-hp elec- 
tric motor. This provides ample power to 
break up any lumps of coal or rock that 
might be caught between the rotor tips 
and the feeder housing. 

The conveying pipeline has a graduated 
diameter beginning at 18 in OD for ap- 
proximately 138 ft, going to 20 in OD for 
the next 693 ft, and ending up at 22 in 
OD for the remainder. This is meant to 
help maintain a constant air velocity 
within the pipeline. Wall thickness is 
0.375 in throughout. Equipment, power, 
and pipeline requirements are based upon 
the experience gained in the experiments 
on vertical hoisting conducted by the 
National Coal Board of Britain 0»,Z~^» 
28 , 30-32) and in the United States', "par- 
ticularly in relation to the blind shaft 
borer (j_6, 23-3A). 

Table 10 shows the (1981) cost of 
this pneumatic hoisting system. Table 11 
shows the cost for a skip hoist system 
capable of handling a similar situation. 
Costs shown for the skip and pneumat- 
ic hoisting do not include sinking the 



shaft; both estimates 
ing shaft. 



assume a preexist- 



OFF-LOADING A TUNNEL-BORING MACHINE 

The tunnel for this application of 
pneumatic haulage is assumed to be 12 ft 
in diameter, driven with a full-face 
borer that produces 50 ton/h at a fairly 
constant rate. Most of the cuttings will 
be minus 2 in. The proposed length of 
the tunnel is 2,000 ft, and it includes 
enough of a bend to obscure vision. 

Equipment for the tunnel boring experi- 
ment is mostly of standard design. The 
rotary air-lock feeder is powered by a 
separate power pack mounted on a common 
skid base with the feeder unit. This 
entire assembly is pulled along with the 
advancing tunnel borer and linked to 
it by flexible couplings. A section of 
telescoping pipe with a 25-ft reach 
bridges the distance between the feeder 
and the material-conveying pipeline. 
When the pipe is fully extended, the 
system is shut down, the telescoping sec- 
tion retracted, and both air and mate- 
rial-conveying pipelines are extended. 



TABLE 10. - Cost estimate of a pneumatic hoisting system 

Positive displacement blowers (2) on skid bases operating in series to sup- 
ply 19,960 cfm air at 15 psi, complete with 2 800-hp motors, gearboxes, 

and starters $197,000 

Infeed equipment to introduce coal into the pipeline: 

Radmark 300A airlock feeder 50,000 

Power pack-control console >, 20,000 

Bases for feeder and power pack 12,000 

Infeed chain conveyor to feeder > 20,000 

50-ton bunker conveyor, complete with automatic controls 110,000 

Total 212,000 

Air and material piping: 

200 ft of 20-in-OD, 0. 125-in-wall, 20-ft-long pipe sections, elbows, 

couplings , flexible connectors 4, 000 

188 ft of 18-in OD, 693 ft of 20-in OD and 419 ft of 22-in OD, 0.375 in 
wall, 20-ft length sections of abrasion-resistant pipe, 2 90° flat-back 

elbows , wedge couplings for flanges and dresser couplings 61 ,000 

Total 65, 000 

Discharge cyclone 40, 000 

Installation costs for the system including shaft level installation of 
blowers, airlock feeder, infeed chain conveyor and bunker conveyor, and 
shaft installation of material pipes (estimated) 250,000 

Grand total 764,000 



33 



TABLE 11. - Cost estimate of a vertical hoisting system 

Hoist, 400-hp, 90-in parallel drum $550,000 

Foundations (100 yd^ concrete at $300/ yd) 30,000 

Installation (15 workers, 6 weeks) 135,000 

2,600 ft of 1-1/8-in rope 16,000 

Building 50,000 

Headframe and skip discharge bin 140,000 

Installation, foundations, etc 140,000 

Shaft guides and sets at 10-ft centers 90,000 

Installation 150,000 

Skip hoisting arrangement and shaft bottom 150,000 

Miscellaneous, including signals, controls, etc.. 60,000 

Total 1 , 51 1 , 000 



Since quick-connect couplings are used, 
this takes a minimum amount of time to 
accomplish. 

The material-conveying pipeline, com- 
posed of 20-ft sections, has an outside 
diameter of 10.75 in and a wall thickness 
of 0.50 in. The air-conveying pipeline, 
from the blower to the feeder unit, has 
0.125-in wall thickness, with 12,75-in 
OD. 

The blower used on this application 
must have 8,112 cfm of air available and 
must convey the cuttings at 14 psi. A 
975-rpm blower powered by a 600-hp motor 



is sufficient. Figure 4 shows the layout 
envisioned for this haulage system. 

The discharge unit is the major differ- 
ence between this and other pneumatic 
systems described. The cuttings could be 
stowed elsewhere in the mine or carried 
to the surface through a borehole, but it 
is assumed that they will be loaded out 
to rail cars for haulage out of the mine. 

The discharge unit designed is a long, 
boxlike structure with a conveyor beneath 
it that moves in the same direction as 
the conveyed material. The air expands 
when it reaches the box allowing the 



3 
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Direction of ventilation 



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Blower unit 



Radmark feeder 
and control unit 



machine 






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FIGURE 4. - Layout of pneumatic transport off-loading a tunnel-boring machine. 



34 



TABLE 12. - Cost estimate of pneumatic conveying equipment to off-load 
a tunnel-boring machine 

Positive displacement blower to supply 8,112 cfm air at 14 psi, complete 

with 600-hp motor and gearbox $52,000 

Infeed equipment to follow tunneling machine: 

Radmark rotary airlock feeder 35,000 

Power-pack control console 18,000 

Sled for feeder and power pack , , 8,000 

To tal 61 , 000 

Air and material piping: 

2,100 ft of 12.75-in-OD, 0.125-in-wall, 20-ft pipes, elbows, telescopes, 
couplings, flexible connectors, 2,000 ft of 10.75-in-OD, 0.5-in-wall, 
20-ft abrasion-resistant pipes, telescopes, wedge couplings for flanges.. 81,000 

Discharge unit 25,000 

Pipe installation cost (as tunnel progresses)..... 5,000 

Supply track 59,700 

Grand total 283, 700 



cuttings to fall onto the belt that loads 
them into the waiting rail cars. The air 
continues to the end of the discharge 
unit where the dust is removed by water- 
jet scrubbers, and the cleaned air is 
exhausted by a fan through ducts to the 
return airway. Because the capacity of 
the fan is greater than the amount of 
air used for conveyance, the discharge 
unit also draws any airborne dust in the 
area of the loader-conveyor into itself, 
providing a relatively dust-free area. 
The sludge from the scrubbers falls 
onto the belt and is carried away by the 
rail cars. 

The entire discharge unit is suspended 
above the rail track by roof bolts or 
other supports at a height sufficient 
to allow the rail cars to pass beneath 
unobstructed. The unit was designed 
with the problem of space in mind. 



Although a cyclone would be more effi- 
cient, it would require removal of a 
large area in the tunnel roof, which 
would add to cost. Table 12 shows the 
estimated (1981) cost of installing such 
a system, and table 13 shows the cost of 
installing a rail system capable of han- 
dling the same amount of coal. 

TABLE 13. - Cost estimate of a rail 
haulage system 

Battery locomotive, 5-ton 

capacity (2 required) $100,000 

Side-dump cars, 3-ton capacity 

(12 required) 78,000 

36-in-gauge rail track, 60-lb 

section 21, 400 

Armored ties at 4-ft centers... 7,100 
Installation cost (as tunnel 

progresses) 10,000 

Total 216, 500 



CONCLUSIONS 



The development of pneumatic haulage 
systems for underground coal has been 
slow in this country, compared with Euro- 
pean countries. Several studies in Eng- 
land, including those at Horden, Fry- 
ston, and Shirebrook Collieries, have 
proven the ability of pneumatics to move 
large amounts of coal vertically as well 
as horizontally, and accomplish the task 
cheaply, efficiently, and safely. The 



primary safety concern has been the 
threat of explosion, since methane and 
coal dust would be trapped within a pipe- 
line and could spark or smolder into 
flame during downtimes. Studies have 
shown, however, that an explosion is 
extremely unlikely if adequate pre- 
cautions are taken; that is, methane 
should be purged from the system before 
startup, tramp iron should be removed by 



35 



» 



a permanent magnet, methane detectors 
should be installed on blowers and feed- 
ers, and electrical interlocks should be 
installed that ensure proper procedures 
are followed before the system is acti- 
vated. In addition to these safety pre- 
cautions, the entire system should be 
designed to withstand, contain, and ex- 
tinguish any flame or explosion that 
might occur. 

Underground haulage has one of the 
worst safety records in the industry, 
second only to ground control in se- 
verity of accidents. Miners are caught 
in, run over by, and crushed by equip- 
ment around which they must work. A 
pneumatic system is a stationary, en- 
closed system with few open moving parts. 
Although accident statistics for other 
methods of haulage are well documented, 
there are no statistics on the safety 
record of pneumatic haulage, primarily 
because it is not a system currently in 
use. However, when comparing the acci- 
dent histories of shuttle cars, convey- 
ors, hoists, or rail haulage, there are 
many areas where pneumatic haulage could 
reduce or eliminate potential hazards. 
Material-handling systems for supplies. 



supports, and personnel will not be re- 
placed by pneumatics. Mechanized traffic 
at the face and in main haulageways could 
be reduced, however, with a corresponding 
reduction in accident potential. 

Several systems have been designed and 
tested to apply pneumatic haulage to 
problems as varied as room-and-pillar 
mining, vertical hoisting, and tunnel de- 
velopment. In all trials, the haulage 
systems have operated successfully and 
safely. Currently, two U.S. mines use 
pneumatic systems for primary haulage. 
Both systems were installed in difficult 
situations where more conventional sys- 
tems had failed. With the new systems, 
cost reductions of 35 to 75 pet were 
realized and production increased up to 
50 pet (23-r5). 

Pneumatic haulage is not a panacea. 
Rail haulage, conveyors, hoists, and 
shuttle cars have established their place 
in U.S. coal mining. The benefits of 
pneumatics, however, should not be over- 
looked. These systems have proved to be 
safe, flexible, efficient, and economi- 
cal, all of which should be of great in- 
terest to mine management. 



REFERENCES 



1. Bowers, E. T., T. Fishburn, C. Ker- 
kering, and P. McWilliams. A User's 
Guide to the ADA Program (Accident Data 
Analysis). BuMines Handbook, 1982, 78 
pp.; available upon request from E. T. 
Bowers, BuMines, Spokane, WA. 

2. Powell, J. E. Pneumatic Transport 
Safety Designs. Final report on BuMines 
contract J0100029 with Radmark Eng. , 
1981, 85 pp.; E. Bowers, BuMines, Spo- 
kane, WA. 

3. Caldwell, L. G. A Pneumatic Con- 
veying Primer. Chem. Eng. Prog., v. 72, 
Mar. 1976, pp. 63-69. 

4. Longmate, C. D. Experiences of 
a Manufacturer of Pneumatic Equipment. 
Colliery Guardian, v. 228, No. 5, 1980, 
pp. 171-116. 



5. Ball, D. G. , and D. H. Tweedy. 
Pneumatic Hoisting From Underground. 
Can. Min. and Metall. Bull,, v. 68, No. 
753, 1975, pp. 59-63. 

6. Powell, J. E., and R. J. Whitfield. 
Construction Industry Applications (of 
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CA, June 26-28, 1978). BHRA Fluid Eng., 
Cranfield, Bedford, England, v. 1, paper 
F6, 1978, 11 pp. 

7. Smith, W. C. Report on Vertical 
Hoisting by Pneumatic Pipeline. Radmark 
Eng., Ltd., Rep. 38, June 1974, 17 pp. 

8 . Daily Telegraph (London) . Blow- 
pipe Lifts Coal to Pithead. Aug. 29, 
1977, p. 4. 



36 



9. Chlronis, N. P. Three Innovations 
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10. Faddick, R. R. , and J. W. Martin. 
Pneumotransport of Tunnel Muck, Pres. 
at Pneumotransport 4 (Carrael-by-the-Sea, 
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F2, 1978, 14 pp. 

11. Brezovec, D. Air System Takes 
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1981, pp. 80-84. 

12. Mason, R. New Methods Speed 
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13. Jackson, D. Coal Moves by Air at 
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1982, pp. 64-67. 

14. Mine Safety and Health Reporter. 
Innovative Coal Transport System Designed 
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Apr. 21, 1982, 1 p. 

15. Brezovec, D. Vacuum Hauls Thin- 
Seam Coal. Coal Age, v. 87, No. 12, 
1982, pp. 76-77. 

16. Radmark Eng., Inc. Build, Field 
Test and Evaluate a Pneumatic Hoist Sys- 
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(Final report, U.S. DOE contract DOE/ET/ 
100038-Tl), 1980, 139 pp. 

17. Powell, J. E. Vertical Hoisting 
Using Pneumatic Conveying Systems. Pres. 
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(Atlantic City, NJ, Oct. 4-6, 1982), 8 
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Mines, Spokane, WA, 

18. Daling, P. M. , and C. A. Geffen. 
Evaluation of Safety Assessment Meth- 
ods for the Mining Industry (contract 
J0225005). BuMines OFR 195(l)-83, 1983, 
123 pp. 



19. Meyerchick, W. D. Continuous 
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1983, pp. 156-158. 

20. Colorado School of Mines Research 
Foundation, Inc. Pneumatic Transport of 
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1963, pp. 55-56. 

21. Kelly, J. E. , and B. L. Forkner. 
Ignitions in Mixtures of Coal Dust, Air, 
and Methane From Abrasive Impacts of Hard 
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BuMines RI 8201, 1976, 19 pp. 

22. Soo, S. L. , J. A. Ferguson, and 
S. C. Pan. Feasibility of Pneumatic 
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July 14-15, 1975). Intersoc. Committee 
on Transport., ASME, 1975, 15 pp. 

23. Reiber, M. , S. L. Soo, and 
J. Stuckel. The Coal Future: Economic 
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and Innovations To Secure Fuel Supply 
Independence - Pneumatic Pipeline. (Pre- 
pared under NSF grant GI-35821). May 
1975, 227 pp.; NTIS PB-247 678/ 6GA. 

24. Litchfield, E. L. Certain Aspects 
of Ignition and Flame Propagation Rela- 
tive to Pneumatic Coal Transport. Pres. 
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CA, June 26-28, 1978). BHRA Fluid Eng., 
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Al , 5 pp. 

25. Johnston, A. G. Comments on E. L. 
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port 4 (Carmel-by-the-Sea, CA, June 26- 
28, 1978). BHRA Fluid Eng., Cranfield, 
Bedford, England, v. 2, 1978, p. 74. 

26. Powell, J. E. Comments on E. L. 
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port 4 (Carmel-by-the-Sea, CA, July 26- 
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Bedford, England, v. 2, 1978, p. 74. 



37 



27. Singh, M. M. , and W. S. Court- 
ney. Application of Pneumatic Stowing in 
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28. Nicholson, J. T. Vertical Pneu- 
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don), V. 138, No. 210, 1979, pp. 657-665. 

29. McAteer, J. C. Miner's Manual, A 
Complete Guide to Health and Safety Pro- 
tection on the Job. Crossroads Press, 
1982, p. 84. 

30. Peters, T. W. Shirebrook Pneumat- 
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dian, V. 225, No. 11, 1977, pp. 853-856. 

31. Onley, J, K. , and J. Firstbrook. 
The Practical Application of Pneumatic 
Transport Techniques to the Raising 
of Mineral From Deep Shafts. Pres. at 



Pneumotransport 4 (Carmel-by-the-Sea, CA, 
July 26-28, 1978). BHRA Fluid Eng., 
Cranfield, Bedford, England, v. 1, paper 
Fl, 1978, 14 pp. 

32. Peters, T. W. Vertical Pneumatic 
Transportation. Colliery Guardian, v. 
228, No. 12, 1980, pp. 556-558. 

33. Firstbrook, J. Operation and De- 
velopment of the Pneumatic Pipeline Coal 
Transportation System. Pres. at Pneumo- 
transport 5 (London, England, Apr. 16-18, 
1980). BHRA Fluid Eng. , Cranfield, Bed- 
ford, England, v. 1, paper A4, 1980, 
pp. 47-74. 

34. Powell, J. E., and K. Ruby. Pneu- 
motransport Applied to Mine Shaft Sink- 
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England, Apr. 16-18, 1980). BHRA Fluid 
Eng., Cranfield, Bedford, England, v. 1, 
paper A2, 1980, pp. 25-34. 



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